1. Field of the Invention
This invention relates to improvements in a method of producing benzamides which are useful for intermediate products of medicines and agricultural chemicals.
2. Description of the Prior Art
Hitherto, benzamides have been able to be produced by reacting ammonia or ammonium salt with benzoic halides, benzoic anhydrides or benzoic acids.
U.S. Pat. No. 3,825,594 discloses a production method for aryl halide having two trifluoromethyl groups in an aryl ring, in which 2,6- or 2,4-bis(trifluoromethyl) benzoic acids are formed into acid chlorides which are subjected to amidation with primary amines. Additionally, a literature (Chemical Abstracts, Vol. 79: 42101, Zh. Org. Khim. 1973, 9(5), 1019-24 (Russ)) discloses that 2,6-bis(carboxytrifluoro methyl) benzene is reacted with SF.sub.4 to produce 2,6-bis(trifluoromethyl) benzoylfluoride which is then reached with ammonia thereby to form 2,6-bistrifluoromethyl benzoic amides. Further, a literature (J. Org. Chem., Vol. 39, No. 23, 1974, 3327-3331) discloses that aryl halides, carbon monoxide and primary or secondary amine are reacted in the presence of a catalytic amount of triphenylphosphine-palladium salt complex thereby to produce corresponding secondary and tertiary amides.
As discussed above, trifluoromethyl benzamides can be produced from acid chloride or acid fluoride of bistrifluoromethyl benzoic acid. However, difficulties have been encountered in the above conventional techniques. That is, the conventional techniques require to prepare the acid chloride or the acid fluoride as a precursor. As a result, a production process of the trifluoromethyl benzamides requires multi-state reaction steps.